The following generally relates to a multifunctional electric tool and, more particularly, to a multifunctional electric tool having an automatic rotational speed adjustment capability.
A multifunctional electric tool enables replacement of different output shafts on the same electric tool. The different output shafts may be equipped with corresponding accessories such as an angle grinding disc of an angle grinder and a polishing pad of a polishing machine. Thus, the electric tool can have different functions by arranging these different accessories. Some of these accessories need to work at a high rotational speed, but some accessories are dangerous at a high rotational speed of operation, and need to work at a low rotational speed. For example, the working rotational speed of the angle grinding disc is generally 11000-12000 r/min, while the working rotational speed of the polishing pad of the polishing machine is generally 3000-5000 r/min. If the accessory does not conform to the working rotational speed set in the electric tool, it cannot work normally. If the rotational speed of the electric tool is interlocked with the accessory installed thereon accordingly, that is to say, if one accessory is replaced, the highest rotational speed of the electric tool will not exceed the needed working rotational speed of the accessory. U.S. Pat. No. 7,431,68 discloses that an accessory is provided with an element for marking the character of the accessory, and a machine body can identify the element and control the machine to operate at a corresponding speed. In the disclosed system, the user needs to buy this special element additionally, which is not convenient for the user. U.S. Pat. No. 5,526,460 discloses that a speed limiting mechanism is arranged on an impacting spanner, thus the operating speed of the device may be set by adjusting the speed limiting mechanism manually. This method limits the rotational speed of the device by manual adjustment, thus it cannot prevent incorrect operation caused by the incorrect operation of the adjustment mechanism.